| With the rapid development of China’s new-type urbanization process,the necessity of developing and using urban underground space is gradually highlighted,and subway plays an indispensable role in this development process.In the process of subway tunnel construction,the safe launching and receiving of shield is the key to the success of the project.At present,the horizontal freezing method has been widely used in shield launching and receiving,and a large number of scholars have studied it.However,due to the complexity and particularity of geological conditions and site,the research on the freezing characteristics of shield receiving horizontal freezing method and its influence on the surrounding environment under complex site conditions is still not systematic.In view of this,relying on the shield receiving horizontal freezing project at the south end of Shuanghehu station of Zhengzhou metro line 17 in the complex environment,this paper analyzes and studies the temperature field and displacement field in the freezing construction process by using the methods of field test,numerical simulation and theoretical analysis,and reveals the variation rules of underground temperature field,surface deformation and existing underground buildings in the complex field The formation law of freezing wall and the influence range of horizontal freezing are summarized.Moreover,the reason why it is called complex environment is that the soil has strong water permeability,the shield passes through the existing underground shopping mall in short distance,the shape of frozen soil is irregular,and the groundwater level is high.The main research contents are as follows:(1)Based on the field test,the temperature field and displacement field of freezing and thawing in complex site are tested,and their changes are analyzed according to the field test results.The temperature change of reinforced soil induced by horizontal freezing,the surface displacement change and the freezing expansion and thawing settlement law of existing underground buildings are revealed.(2)Based on the numerical simulation,the overall analysis model considering the“ring” horizontal freezing zone,frozen soil and existing buildings is established,and the change law of freezing and thawing temperature field and the development law of freezing curtain are studied.The results of field measurement and numerical simulation of frozen reinforcement area,surface and existing underground commercial street during freezing construction are compared and verified to further reveal the change and development law of temperature field of frozen soil caused by circular horizontal freezing reinforcement.At the same time,the thermal physical parameters are changed to control and analyze the freezing temperature field.The results show that the larger the thermal conductivity is,the smaller the specific heat capacity is,the smaller the phase change latent heat is,and the faster the freezing temperature is,which provides the optimization design basis for similar projects.(3)Based on the finite element model of freezing temperature field,an overall analysis model of frost heave of irregular rock and soil mass surrounded by shield tunnel,existing underground shopping mall and station side wall is established for horizontal freezing reinforcement.The change law of displacement field of frozen rock and soil during freezing period is revealed,and the influence of freezing and shield tunneling on existing underground shopping mall is analyzed.At the same time,based on the single circle multi pipe frost heave deformation model,the change law of surface displacement is further revealed from the theoretical analysis,and the main influence range of frost heave vertical displacement is pointed out,which provides guidance for the actual construction.(4)Based on the above research and analysis,comprehensive deformation control measures are proposed for horizontal freezing method of shield tunneling in such complex environment. |
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